Do suicide rates climb at high altitudes?

NEW YORK (Reuters Health) - Suicide rates may be higher up where the air is thinner, hints a new study.

Further, researchers found that the effect of elevation was strong even after accounting for ratios of guns to people, as well as people to land.

"I was struck by the fact that suicide rates were much higher in the Rocky Mountain region and did not feel that the existing theories -- increased gun ownership or lower population density -- were necessarily adequate to explain the phenomenon," senior researcher Dr. Perry F. Renshaw of the University of Utah, in Salt Lake City, told Reuters Health by email.

Approximately 12 of every 100,000 Americans commit suicide every year, according to the U.S. Centers for Disease Control and Prevention. Looking solely at the intermountain West states, from Montana to New Mexico, those annual rates rise to between 14 and 20 of every 100,000 people.

Renshaw and his colleagues collected and analyzed a range of U.S. data in an effort to tease apart the influence of altitude from the other potential suicide risks factors that are known to be more common in mountainous areas.

Altitude did appear to affect the numbers of people taking their own life, report the researchers in The American Journal of Psychiatry.

"At 2000 meters in altitude -- the approximate altitude of Colorado, Wyoming, and Utah -- suicide rates appear to be elevated by about 70 percent relative to rates at sea level," said Renshaw. "In Utah, where I live, this would account for between 100 and 150 extra suicide deaths each year."

After adjusting for gun ownership and population density, both also significant predictors on their own, the team found that altitude of residence still strongly influenced suicide rates. All three factors taken together explained about 69 percent of the differences in suicide rates across the 48 contiguous states.

The researchers caution that their results do not necessarily mean altitude drives one to commit suicide. They note the possibility of additional players in suicide risk, such as economic and cultural factors.

"We observed very similar findings in South Korea, which makes a cultural explanation less likely," Renshaw added.

So what could be tying elevation to suicide? Renshaw's best guess is that the stress associated with the lack of oxygen found at higher elevations might negatively affect some people with pre-existing mood disorders.

"If one accepts that life at an increased altitude is a risk factor for suicide, it becomes much more important to determine the mechanism that accounts for this association," Renshaw said. "This knowledge would lead directly to novel treatment strategies for at-risk individuals."